1. Field of the Invention
The present invention relates to a sheet supply apparatus for supplying a sheet (recording sheet, original sheet or the like) in an image forming apparatus such as a facsimile, a copying machine, a printer and the like.
2. Related Background Art
In the past, there has been proposed a sheet supply apparatus for supplying a recording sheet in a facsimile machine and the like, wherein the sheets are separated one by one by a sheet supply roller and a double-feed preventing member (separation pad) urged against the sheet supply roller. In such a separating mechanism, when certain kinds of sheets are used, vibration and noise may be generated between the sheet supply roller and the separation pad. To prevent such noise, there has been proposed a mechanism in which a separation pad has two rubber layers, for example, as disclosed in the Japanese Utility Model Publication No. 3-12755.
This mechanism has a laminated-structure friction pad comprising a friction layer made of urethane rubber, and a buffer layer made of elastic material softer than the urethane rubber. The sheets are separated by the friction layer and the vibration is suppressed by the buffer layer, thereby preventing the noise.
However, in the above-mentioned conventional separating mechanism, since the two-layer friction pad is constituted by the two rubber layers bonded together by an adhesive, the manufacturing cost is increased. Further, since the buffer layer is made of softer elastic material such as foam rubber, foam polyurethane, polyurethane foam or the like, after the separation pad was used for a long time, the elasticity of the buffer layer is worsened to cause the plastic or permanent deformation. If the permanent deformation occurs, pressure (separation pressure) between the sheet supply roller and the friction layer is decreased and/or a contacting condition between the sheet supply roller and the friction layer is changed from the initial condition, thereby worsening the sheet separating ability.